fix: sshfs polling, WebSocket broadcast, prompt progress bar, resizable stats panel

- log_watcher: add --reopen-log mode (close/reopen each poll) for sshfs/network
  filesystems; fix nonlocal clients bug causing UnboundLocalError on first broadcast;
  fix list(clients) copy to prevent RuntimeError on concurrent set mutation
- log_parser: capture progress=X.XX from prompt timing lines into Metrics.prompt_progress
- frontend: show progress bar during processing_prompt state with PROMPT N% label;
  widen stats panel to 300px; remove model name truncation; add drag handle on
  right border of stats panel to resize between 280px–840px

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/index.html

@@ -116,6 +116,7 @@
 
     <!-- ── Stats panel ────────────────────────────────────────────── -->
     <div id="stats-panel">
+      <div id="resize-handle" title="Drag to resize"></div>
       <div class="stat-row" id="row-model">
         <span class="sk">MODEL</span>
         <span class="sv" id="sv-model">—</span>